A common type of truck tailgate lift comprises a rectangular load platform pivotally connected at a forward edge to the swingable rear ends of a pair of parallelogram linkages. The forward ends of the linkages are secured to the bed, frame or chassis of the truck and a power means, typically an electrical hydraulic system, is provided for raising and lowering the load platform relative to the bed of the truck. The parallelogram linkages maintain a substantially horizontal, active attitude of the load platform during freight handling operations. When not used for loading purposes, the load platform is turned upwardly to substantially vertical attitude to a transit position in which it may also serve as the closer for the tailgate opening of the truck body.
In the past, a variety of mechanisms have been developed for turning the load platform between horizontal and vertical positions by the use of either the power cylinder or cylinders that raise and lower the liftgate or the use of a dedicated, separate power cylinder or cylinders. One commonly used approach in the former arrangement uses a spaced apart pair of cam blocks on the rearwardly facing vertical surface of the sill of the truck bed which are engagable by a spaced pair of cam followers mounted to the forward edge of the load platform. The present invention is an improvement over all of these systems.